Two-division telephone system.



PATENTED APR- 3, 1906- H. M. POST.

TWO DIVISION TELEPHONE SYSTEM.

APPLICATION FILED 0012 24, 1902. v

2 SHEETS-SHEET 1.

PATENTED APR. 8, 1906;

H. M. POST. TWO DIVISION TELEPHONE SYSTEM.

APPLICATION FILED 00124, 1902- 2 SHEETS-SHEET 2.

UNITED STATES PATENT QFFIGE.

HOWARD M. POST, OF CHICAGO, ILLINOIS, ASSIGNOR TO KELLOGG SWITCHBOARD AND SUPPLY COMPANY, OF CHICAGO, ILLINOIS,

A CORPORATION OF ILLINOIS.

TWO-DIVISION TELEPHONE SYSTEM.

Specification of Letters Patent.

iratenteol April 3, 1906.

Application filed October 24, 1902. Serial No. 128,528.

To all whom it may concern:

Be it known that I, HOWARD M. Posr, a citizen of the United States of America, residing at Chicago, in the county of Cook and State of Illinois, have invented new and useful Improvements in Two-Division Telephone Systems, of which the following is a specification.

My invention relates to a divided multipleswitchboard system, my object being to provide a system of this type in which the sources of energy are all located at the central ofiice, in which a minimum amount of apparatus for each line is required, and in which only two wires extending throughout the switchboard are employedfor each line, and, further, to provide in such a system suitable apparatus for connecting the subscribers together and for properly supervising and attending the connections.

The advantage of the divided central system is well understood at the present date and chiefly resides in the fact that the multiple sections of the switchboard are greatly reduced at the expense of only a slight increase of other apparatus for the lines. The general plan is for each subscriber to be represented upon each division of the switchboard by means of an answering-jack and line-signal and to have only upon one of said divisions multiple jacks or connection terminals. The subscribers then instead of being known merely by a number, as in the ordinary system, are listed in the directories by means of numbers and in addition the division name or letter upon which their multiple-jacks are placed, whereby connections are always completed by the operator with the'lines upon one division, but may be initiated by the subscriber at any of the divisions. My invention corresponds to this general type, but is designed more particularly for a two-division system. The apparatus is so arranged that but two relays are required for each line at the central ofhce, whereby a great saving resultsin the cost of installation and mainte nance. The subscribers have two push-buttons corresponding to the two divisions, whereby they are enabled to operate their sig nal upon either board. The signals are arranged to be locked in operating position as soon as the push-buttons are operated,whereby the signals remain exposed until the operator answers, even though the push-buttons be released. The circuits are arranged for the ready application of pilot signals without complication of parts.

Other novel features and advantages will be brought out in connection with the detailed description and the claims.

My invention is illustrated in the accompanying drawings, in which the same reference characters are used throughout to designate like parts, and in which Figure 1 is a diagram of a telephone system embodying my invention. Fig. 2 is a diagram of a modification, and Fig. 3 is a diagram of still another modification.

The switchboard is shown as having two divisions, which may be termed A and B divisions. TWO subscribers lines L and L are shown extending from their respective substations D and D to the central office. At the substation the subscriber is rovided with the usual common battery su scribers set, the set shown in the drawings being intended merely to typify any of the usual or desired apparatus. A switch-hook 4, which normally carries the receiver 5, is adapted to open a bridge of the line containing said receiver and the transmitter 6. A call-bell 7 and condenser 8 are permanently connected between the two line-wires.

In the tip-conductor 2 a key or push-button switch 9 is provided, which is adapted, when depressed, to open said conductor and ground the same, and a similar push-button or key 10 is provided to open and ground the line conductor 3. The line conductor 2 is permanently connected with the spring 11 of a relay R, the normal contact 12 of which is connected, by means of conductor 13, with one winding 14 of relay R ,which winding is connected, by means of conductor 15, with the individual signal-lamp S for the line, located upon the A division of the switchboard. The circuit is then extended by conductor 16 from the other terminal of the lamp, a portion of said conductor being common to a plurality of lines and the common portion including the pilot-relay R to point 24, and thence by conductor 17 with the live pole of common battery B, the opposite pole of which is grounded. The other line conductor 3 is permanently connected with the spring or movable contact 18 of the relay R 1 a conductor with one winding 21 of the re- 1 lay R and thence by conductor 22 to the signal-lamp S for the line, located in the B division of the switchboard. The other terminal of the lamp is' connected with the conductor 23 common to a plurality of lines and including the winding of the pilot-relay R this conductor being also oined at the point 24 with the conductor 17, leading to the battery B The relay R is provided with a second movable contact 25, the normal contact 26 of which is grounded and the forward contact 27 of which is connected to the j unction-point 28 upon the conductor 20. This movable contact is joined by conductor 29 to a similar movable contact 30 of the relay R the normal contact 31 of which is likewise grounded and the forward contact of which is connected to the junction 33 upon the conductor 13. The forward contact 34 of the spring 11 of relay R is oined by conductor 35 with the tipspring of the answering-jack J located upon the B division of the switchboard, while the normal contact 36 of the spring 18 of relay R is connected byconductor 36 with the sleevecontact of said answering-jack J Conductors 37 and 38 connect the conductors 35 and 36*, respectively, with the tip and sleeve contacts of the answering jack J, located upon the A division of the switchboard. The multiple jacks J and J for the said line are located upon the B division of the switchboard and are connected by conductors 39 and 40 to the conductors 35 and 36, whereby the tip and sleeve contacts of all the jacks upon all of the boards are connected in multiple with each other. The junction-point 41 upon the sleeve-conductor 36 is connected with one terminal of the winding 42 of the relay R which winding is connected through the intermediation of conductor 43 with a similar winding 44 of relay R, the other terminal of which winding is grounded. The pilot-relay R located in the A division of the switchboard, controls through its normally open contacts the circuit of the pilot-signal S said signal being common to a plurality of lines. Similarly, the pilot-relay R located upon the B division of the board, controls through ,its normally open contacts the pilot-lamp S.

The line L is provided with exactly similar apparatus, except that the multiple jacks J and J for the line are shown located upon the A division of the switchboard. The construction and operation, however, remain the same.

The operator's apparatus, which is intended to be used at the various sections or divisions of the switchboard, is indicated in the diagram by the single apparatus at the A division. The cord-circuit comprises the answering-plug P and the calling-plug P each provided with tip and sleeve contact surfaces adapted to register with the like contion terminals of the lines when the plugs are inserted therein. The tip contacts of the plugs are connected together by the tipstrands t and t and the interposed condenser 0, while the sleeve-contacts are likewise connected together by the flexible strands s and s and the interposed condenser 0 A battery B is bridged across the answering end of the cord-circuit upon that side of the condensers, the connection to the tip-strand including the winding of the supervisory relay 1", while the similar connection to the sleeve-strand from the opposite pole of the battery includes the winding of the supervisory relay 1' The relay 1" controls the nomrally closed contacts and the relay r the normally open contacts of the local circuit of the supervisory signal S associated with the answering-plug P. A like arrangement exists for the calling end of the cord-circuit, a battery B being bridged thereacross and including upon one side the winding of supervisory relay 1" and upon the other that of supervisory relay r These relays, as before, control the local circuit of the supervisory signal-lamp S, associated with the calling-plug For testing purposes the forward portion of the tip-strand of the cord-circuit is connected with the movable contact 45 of the sleeve supervisory relay 7*, the forward contact of which is adapted to complete the said tip-strand t when the relay is energized, but the normal contact of which is connected by a conductor 46 with the high-impedance and high-resistance test-relay r, the opposite ter minal of which is grounded by branch 47. This relay when energized closes a ground branch 48 from one side of the transmittercircuit, which permits a flow of current from the battery B and inductively causes abusyclick in the operators receiver. The operators receiver 49, together with the secondary winding of her induction-coil 50 and a condenser 0 are adapted to be bridged across the calling end of the cord-circuit by means of the keys 51 and 52, these keys being merely diagrammatically intended to indicate any usual or desired form of listeningkey and which is usually operated by means of a single lever. The operators transmitter 53 is grounded upon one side by conductor 47 and is connected upon the other through the impedance-coil 54 and conductor 55 with the common conductor 56, leading to the live pole of battery B The primary of the operators induction-coil and the condenser c are connected in shunt of the transmitter 53.

A ringing-generator 57 is adapted to be connected between the ground and the tipstrand of the cord-circuit by means of the ringing-key 58 60, a resistance-lamp 59 being included between the generator and tip-key 58 to cut down the current and the corresponding sleeve-key 60 being adapted when tact-surfaces of the spring-jacks or connecl actuated to close a circuit through the re- 13o sistance 61 and the branch 62 and the common conductor 56 to the battery B whereby the relays R and R are maintained operated during ringing.

The operation of my invention is as follows: The calling subscriber would first ascertain the division upon which the wanted subscriber is listed in the directory of the exchange and would then push the button corresponding to that division, the buttons be ing lettered in accordance with the names of the two divisions as, for instance, A and B. If it be desired to operate the signal located upon the B division of the switchboard, the button is depressed, thus grounding the line conductor 3, and thereby completing a circuit from the live pole of the battery B over conductor 17, point 24, conductor 23, including the winding of pilot-relay R the line-lamp S conductor 22, winding 21 of relay R, conductor 20, contacts 19 and 18 of relay R and over conductor 3 to ground at the substation. The current in this path is sufficient to actuate the relay R to close a locl ingcircuit for itself, said locking-circuit being completed from point 28 or conductor 20, contacts 27 and of the relay R,conductor 29, contacts 30 and 31 of the relay R to ground, this locking branch being in parallel with the line conductor 3, and therefore replacing it in the further operation of the said signal and relay. If the resistance of the line conductor is so great as to prevent the full operation of the lamp S over the path first completed, the substitute path over the locking-circuit being entirely local is of low enough resistance so that the current flowing brings the lamp up to full illumination and operates the pilot-relay R The pilot-signal 8, located before the operator upon the B division, is also lighted by current from the battery B Assuming, however, that the wanted subscriber is listed upon the A division, the subscriber would depress the button 9 at the substation, which serves to ground the line conductor 2 at the substation, and thereby completes a path for current from the live pole of the battery B over conductor 17, point 24, conductor 16, including the pilot-relay R the linelamp S, conductor 15, winding 14 of relay R conductor 13, spring 11 of relay R, and conductor 2 to ground at the substation. The current flowing over this path is suflicient to operate the relay R to cause it to attract its spring 30, and thereby closes a locking-circuit for itself from point 33, contacts 32 and 30 of the relay R conductor 29, spring 25 of relay R, the contact 26 to ground, this portion of the looking-circuit being in parallel with the line conductor 2, whereb the button 9 may be released by the subscriber and the said relay remains actuated. The line-lamp S and the pilot-relay R are included in the first-named circuit; but the local circuit is immediately completed by the said locking branch and is of sufficiently low resistance to permit the lamp to be fully actuated. The pilot-lamp S is also actuated by current from the battery B The operator attending the answering-jack of the line L upon the A division upon seeing the signals exposed inserts the answering-plug P of her cord-circuit into the jack J and depresses the listening-keys 51 52 to connect her telephone with the cord-circuit and receives the order from the subscriber. The insertion of the plug P completes another path for current from the battery B through the sleeve supervisory relay W, the sleeve-strand s, sleeve-contacts of the plug and jack, conductors 38 and 36 winding 42 of relay R conductor 43, the winding 44 of relay R to ground over which path current flows to actuate relays R and R as well as supervisory relay T The actuation of the relay R breaks the locking-circuit of the relay R between the contacts 25 and 26, and therefore the local circuit of the line-lamp S and the pilot-relay R and the relay R is also actuated to prevent any possible lighting of the line-lamp S upon the other division of the switchboard. At the same time the springl 1 of relay R and spring 18 of relay R engage their forward contacts 34 and 36 and complete the metallic talking-circuit from the line conductors 2 and 3 to the conductors 35 and 36*, leading to the jacks or connectionterminals upon both sections of the switchboard. The actuation of the supervisory relay r at this time closes a circuit of the supervisory signal S associated with the answeringplug, but the subscribers receiver being off the hook '4 at this time a path for current from the battery B over the metallic line to the substation is now provided, which current finds a path through the tip supervisory relay 1*, which is actuated, and therefore opens the circuit of said supervisory signal S to cause it to remain inert. Upon learning the number of the party wanted the operator proceeds to test the condition of the wanted line. This is done by touching the tip of the calling-plug P to the test-ring of one of the multiple jacks of the line. If the line is not busy, no path for, current will be completed; but if connection has been established with the line at any division of the switchboard the sleeve-conductor 36' will be connected with the live pole of the common battery B or such other battery as may be connected with the sleeve-strand of the oord-circuit used for established connections. WVhen the line is tested, therefore, a complete path for current will be established from the sleeve-conductor of the line and the sleeve-contact of the jack, which is its test-ring, the tip of the testing-plug, the forward portion of the tipstrand 25 thereof, spring of sleeve supervisory relay r conductor 46, the high-resistance and high-impedance test-relay T and conductor 47 to ground. This test-relay, owing to its impedance, builds up its current slowly, and therefore prevents a sudden variation of current upon the tested line, and owing to its high resistance prevents also a large variation of current thereon, whereby the effect of the test is practically unnoticeable to the subscriber or subscribers upon the tested line. The test-relay responding to this current closes a path for current from the live pole of the battery B conductor 56, conductor 55, through the retardation-coil 54, the primary of the operators induction-coil 50, the spring of said relay 7*, and conductor 48 to ground. This will inductively produce a click in the operators receiver, which click may be reduced to any desired extent by varying the resistance of this circuit. If the line is idle, the plug is inserted in the proper multiple jack and the ringing-key 58 60 actuated. The insertion of the plug closes a path for current from the battery B over the sleeve of the cord-circuit, over conductors 40, 38, and 36 the winding 42 of relay R conductor 43, winding 44 of relay R to ground, thus actuating both relays and rendering the line-signals at both divisions of the board inoperative and also connecting the switchboard section or cables of the line to the external line conductors. The operation of the ringing-key does not effect any rearrangement of the relays R and R for the reason that the key 60 closes a circuit from the battery B over the conductor 56, conductor 62, and through the resistance 61 to the sleeve-conductor 40. The path for ringingcurrent is through the resistance-lamp 59, the tip side of the line to the substation, through the condenser and bell at said station, and back over sleeve-conductor 3, conductors 36 38, and 40, and through the resistance 61, conductors 62 and 56 through the battery B to ground. Upon releasing the ringing-key the supervisory relay 9" is actuated over the sleeve side of the connection and. serves through its spring 45 to disconnect the test relay r and to complete the tip-strand of the cord-circuit through its forward contact. It also closes the local circuit of the supervisory lamp S,which is lighted before the subscriber D responds, thus indicating to the operator that he has not yet responded. When the subscriber in answer to his call takes up his receiver, a path for current from the battery 13 over the metallic line is provided and the tip supervisory relay r is actuated to open the circuit of the supervisory lamp S, thus rendering the same inoperative, which indicates to the operator that the subscribers are in communication. At the termination of the conversation the receivers are returned to their respective hooks, with the result that both tip supervisoryrelays in the cord-circuit are deenergized, the corresponding sleeverelays remaining en ergized over the local circuits, and the lamps S and S are lighted to indicate to the operator that the conversation has terminated, when the plugs are withdrawn and all parts restored to normal condition.

Instead of a single station upon each line the lines may be of the polystation type, it being merely necessary to provide each station with a duplicate of the apparatus shown at stations B and B The ground connections referred .to hereinbefore may be and in practice usually are the common oflice grounds or common oflice return. More than two sets of batteries may be employed, if desired, or all the apparatus at both ollices may be operated from the same batteries, as is intended to be indicated in Fig. 1 of the drawings. The cord-circuit at the B division of the switchboard is not indicated in full, for the sake of clearness of illustration; but it will be understood that the same type shown at the A division is intended. to be employed at both divisions. It is thus also seen that the operation of one line-relay opens the circuit of the other linerelay from the substaticn, so that it cannot be simultaneously operated.

In Fig. 2 substantially the same arrangement exists, except that the line-signals S and S are not placed directly in the path for current over the line conductors when the subscriber is calling the central o'l'l'ice. In this arrangei'nent when the subscriber presses one of the calling-keysfor exaniple, key 9 a path for current is provided over the line conductor 2, spring 11 of relay R, conductor 70, winding 14 of relay R and thence by conductors 7 land 72 to the live pole of the common battery B This suffices to operate the relay R which closes its spring 30 upon contact 32, thereby completing a path for current from the battery B over conductors 72 and 71, the winding 14 of relay R point 33, contacts 32 and 30 of the said relay, conductor 29, spring 25 of relay R, its normal contact 26, and thence by conductor 73 to the line signal S, and thence to the pilot-relay R and by way of conductors 74 and 75 to ground. The line-signal S and the pilot-relay R are therefore operated over this local circuit, which local circuit serves to lock the relay R in actuated condition. The pilot-si nal S has its local circuit closed from the main battery B through the normally open contacts of the said. pilot-relay. Upon establishing a connection with the line a path for current is provided over the sleeve-conductor of the jacks, the conductor 36 winding 42 of relay R conductor 43, the Winding 44 of relay R to ground, thus operating both relays R R to open the circuits of the signal-lamps and to render them inoperative and to connect the line conductors 2 and 3 with the jackconduetors. Upon operating the other key at the subscribers station a similar path is es- TIC tablished over the other line conductor and results in operating the corresponding signals and relays.

Fi 3 shows still another modification in whic substantially the same arrangement exists, except that an additional set of contacts are provided upon the relays R and R, with the result that the locking-circuits for the calling-relays and the local circuits for the signals are entirely distinct. Operating the push-button 9 at the substation, for example, closes a path for current over conductor 2, the spring 11 of relay R, conductor 70, winding 14 of relay R and over conductors 71 and 72 to the battery B A spring 30 of the cut-off relay R then closes upon its forwardcontact and completes the locking circuit of the aforesaid relay through the conductor 29 and the additional contact 75 of the relay R to ground. The auxiliary contact 76 of relay R closes upon its forward contact, and thereby completes the local circuit of the signaling-lamp S and the pilot-relay R the circuit being completed from the conductor 7 3, the forward contact of spring 76, and thence by conductor 77 and spring 25 of relay R to ground. This arrangement, as before stated, results in keeping the lockingcircuits for the said relays and the local circuits for the lamps entirely separate. It is of advantage under certain conditions of use. Of course in this arrangement it will be necessary to reverse the ground connections in the cord-circuits.

WVhile the proportions of the several parts used in my invention are not the essence of the same, I have found good results in the ar rangement shown in Fig. 1 with the windings 14 and 21 of relays R and R of one hundred ohms resistance, with ten-volt signal-lamps S and S twentyfourvolt pilot-lamps S and S and batteries B and B of twenty-four volts. The windings 44 and 42 of said relays may be two hundred and fifty ohms each. In Fig. 2 about the same dimensions may be employed, except that the lamps S and S should be twenty-four-volt lamps. In Fig. 3 the same dimensions may also be employed, except that the windings 14 and 21 of the relays R and R may be five hundred ohms resistance each.

While I have described only three methods for carrying out my invention, it will be obvious that many other variations may be made therein and still not depart from its scope or principle.

I claim 1. In a telephone system, the combination with a telephone-line, of a plurality of relays therefor at the central ofiice, parts controlled by said relays and means for causing the operation of said relays singly from the substation and simultaneously from the central office, substantially as-described.

2. In a telephone system, the combination with a telephone line, of two relays only therefor at the central ofiice, parts controlled by said relays and means for causing the operation of said relays singly from the substation and simultaneously from the central office, substantially as described.

3. In a telephone system, the combination with a telephone-line, of a plurality of relays therefor at the central ofiice, means controlled from the substation for operating said relays singly to produce different signals at the central office and means controlled from the central office for simultaneously operating both said relays to render said signals inoperative, substantially as described.

4. In a telephone system, the combination with a telephone-line, of two relays therefor at the central ofiice, means controlled from the substation for singly operating said relays to produce different calling signals at the central office, and further means controlled at the central ofiice for operating both said relays to render said signals inoperative, substantially as described.

5.. In a two-division exchange, the combination with a telephone-line extending from a substation to the central office, of a calling signal for the telephone-line in each division of the switchboard, two relays for the line each controlling one of said signals, means for singly operating either of said relays from the substation to actuate the corresponding signal, and means for operating both of said relays when connection is established with the line at either of said divisions to render said signals inoperative, substantially as described.

6. In a telephone system, the combination with a telephone-line extending from a substation to the central oflice, of two relays for the line at the'central office, switches at the substation, one for each relay, adapted when actuated to close a circuit of the corresponding relay so as to operate the same, and means at the central office for causing and controlling the operation of both said relays, substantially as described.

7. In a telephone system, the combination with a telephone-line, of two line-signals for the line located at different places in the switchboard, a relay for each said signal associated with the line, means at the substation for closing the circuit of said relays individually so as to selectively operate the said signals, and further means for closing an operating-circuit of both said relays when a connection is established with the line at the central oflice to actuate both relays to thereby render said signals inoperative, substantially as de scribed.

8. In a telephone system, the combination with a telephone-line, of a air of relays therefor at the central oflice, teFephonic apparatus controlled by said relays, a central source of current located at the said oflice, means at the substation for closing a circuit from said source through either of said relays, and means for operating both said relays when a connection is established with the telephoneline, substantially as described.

9. In a telephone system, the combination with a telephone-line, of a pair of relays therefor at the central oflice, telephonic apparatus controlled by said relays, a central source of current at said oflice, means at the substation for closing a circuit from said source through either of said relays, and means at the central oflice for closing a circuit from said source through both said relays, substantially as described.

10. In a telephone system, the combination with a telephone-line, of a pair of relays therefor, each of said relays having two windings, telephonic apparatus controlled by said relays, means at the substation for closing a circuit for current through one winding of each of said relays so as to operate them singly, and means at the central office for simul taneously closing a circuit through the other windings of both said relays to operate them jointly, substantially as described.

11. In a telephonaexchange, the combination with a telephoneline, of a pair of relays therefor, telephonic apparatus controlled by said relays, means at the substation of the line for actuating either of said relays singly, a locking-circuit for each of said relays, and means for energizing both of said relays simultaneously when a connection is established with the line at the central office, substantially as described.

12. In a telephone-exchange, the combination with a telephone line, of two relays therefor, telephonic apparatuscontrolled by said relays, means for energizing one of said relays over one line conductor and for energizing the other over the other line conductor, the energizing of one of said relays from the substation serving to open the path for cur rent from the substation through the other relay, whereby the actuation of one relay prevents the simultaneous actuation of the other from the substation, and means for actuating both of said relays when a connection is established with the line at the central o'flice, substantially as described.

13. In a telephone system, the combination with a telephone-line, of two relays therefor at the central office, telephonic apparatus controlled by said relays, means controlled from the substation for energizing one of said relays over one line conductor and the other relay over the other line conductor, said relays serving when so actuated to open the substation circuit of the other relay, whereby both relays cannot be simultaneously actuatedfrom the substation, a lockingcircuit for each of said relays completed through normal contacts of the other relay,

and means for operating both relays when a naling devices inoperative, substantially as described.

15. In a telephone system, the combination with a metallic telephone-line, of a relay, a line'signaling device and a source of current in series in the order named in each line conductor; a portion of the conductor between the source of current and the signaling devices being common to a plurality of lines, and a pilot-signaling device located in said common portion, substantially as described.

16. In a telephone system, the combination with a metallic telephone-line, of two signals therefor at the central office located upon different divisions of the switchboard, two relays for the line adapted to be singly operated from the substation to actuate either of said signals selectively, and means when a connection is established with the line for operating both of said relays to render said signals inoperative during the connection, the path for current for said oper ation of the said relays including a portion of the talking-circuit, substantially as described.

17. In a telephone system, the combination with a metallic telephone-line, of line signals therefor located upon different divisions of the switchboard, two line-relays for the line adapted to be singly operated from the substation, one of said relays controlling one of said signals and the other controlling the other signal, and means when a connec tion is established with the linafor operating both of said relays over a local circuit including a portion of one side of the talking circuit, substantially as described.

18. The combination with a telephoneline, of normally disconnected connectionterminals for the line at'the central office, a pair of signals for the line at the central office, two relays also at the central office and adapted to'be singly operated from the substation to control the operation of either of said signals, and means to operate both of said relays when connection is established with said lines to render said line-signals inoperative and to connect the normally disconnected connection-terminals with the line, substantially as described.

19. In a telephone-exchange, the combination with a telephone-line, of two relays therefor, a signal controlled by each relay, means at the substation of the line for controlling the actuation of either of said relays serving a connection is established with the central olfice, substantially as tially as desIiribed.

21. n a telephone system, the combination with a telephone-line, of two signals selectively, connections W1 th inoperative during the connection, said source eing included in the metallic talking-circuit to h subscribers station central oflice, two relays to be operated from said source, means at the substation to cause the operation of said relays singly, a cord-circuit at the central office to establish connections with the line for conversation, and means for including said source and both relay cal circuit including circuit when a connection is established for conversation, whereby said relays are operated to render the signals inoperative during a connection and the said source is included both of said in the metallic circuit of the line to furnish current for conversation, substantially as described.

23. In a telephone system, the combination with a telephone-line of signals therefor located upon different divisions of the switchand a cord-circuit at the central 'ofiice adapted when connected with the ine for converthrough both relays to simultaneously actuate them and thereby prevent the operation of said signals, said source being also connected with the telephone-line to furnishcurrent to the substation for talking, substantially as described.

24. n a telephone system, the combination with a telephoneline, of a pair of signals therefor at the central ough one Winding of each of said relays to operate them singly, a cord-circuit to estab lish connections with the line for conversation at the central oflice, a source of current associated with the cord-circuit to furnish current to the substation for talking, and means for including said current source and the said other windings of both relays in a local circuit when a connection is established whereby both relays are actuated during the connection, substantially as described.

25. In a telephone system, the combination with a telephone-line, of a signal therefor upon the different divisions of a divided having a local circuit completed ough normal contacts of the relay of the other signal, and means for operating both HOI/VARD M. POST.

Witnesses ROBERT LEWIS AMES, GAZELLE BEDER. 

